Understanding CHEMICAL LESIONS

Mechanism of a chemical burn

The specificity of chemical burns is the partial or complete destruction of the molecules, the cells or the structure of the skin or the eye induced by either an irritant or a corrosive chemical product. The burn degree is determined by the subsequent modification of the tissues.

Development of chemical burns

1. Which chemicals induce chemical burns ?

   
   

   Corrosive and irritant agents are the two categories of hazardous chemicals which can induce chemical burns after a single contact with the eye or the skin.
   Some of them represent a double hazard because they combine a generalized toxic action with a primary corrosive attack (see hydrofluoric acid).

   
   

2. Mechanism of chemical burn injuries

   
   

   Corrosive and irritant chemicals can create an exchange with the constituents of the eye or the skin, which results in chemical burns.

   

   
   

   The six kinds of aggressive chemical reactions supporting this exchange are: acid, basic, oxidation, reduction, chelation of magnesium or calcium and solvatation.

   
   

3. The different steps of a chemical burn

   
   

   The mechanism of burns breaks down in three stages:

   • the contact which is the origin of the burn
   • the penetration
   • the reaction which constitutes the burn.
   
   

   Depending on the nature of the chemical involved, there is a gap lasting from a few seconds to a few minutes only between the time of contact and the time of reaction, in which an efficient intervention is possible.

   
   

4. Some factors affect the severity of burns:

   
   
   • the nature of the chemical
   • its concentration
   • the duration of contact
   • the temperature of the aggressive product.
   
   

In conclusion, the efficient decontamination of any kind of chemical splashes requires:

1- to remove chemical from contact surface to avoid further penetration.
2- to polyvalently stop the six kinds of aggressive chemical reactions.
3- to be able to stop the penetration of the aggressive product into the tissues.
 

How does HF present a specific hazard ?

Hydrofluoric acid has a dual action:

• a corrosive action due to the acid ions (H+), which can damage the superficial tissues (such as corneal epithelium or epidermis),
• a toxic action due to the F- ions, which can deeply penetrate thanks to the acid destruction of the superficial layers of the skin or the eye, and can chelate calcium and thus disturb the biological balances, which leads to more or less deep physiological disorders.

By definition, fluorides in acidic medium (such as boron trifluoride, for instance) carry the same kind of hazard.

Advantages of an active rinsing with the HEXAFLUORINE® solution

Because of this specific hazard and in addition to its sweeping effect, an efficient rinsing must quickly and simultaneously:

• stop the further spread of the aggressive agent that has yet penetrated into the tissues
• remove the chemical thanks to the flow of osmotic pressures
• absorb all the aggressive potential of the chemical product (H+ et F- )

These three properties define the concept of active rinsing.

For decontamination to be optimal, the three above criteria must be gathered.

Today the HEXAFLUORINE® solution is the only solution that contains a molecule meeting such requirements worldwide.

Worsening factors in chemical burns

So, chemical burns result from the chemical reaction between a corrosive or irritant molecule and one or several biochemical constituents of the skin or the eye.

The severity of chemical burns mainly depends on:

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  the nature and concentration of the chemical product in presence:

  
  

  It may react with the human body through different kinds of reactions: acid or basic reaction, oxido-reduction… A product is harmful when its concentration is higher than 0.2N.

   

  
  

• 

  the energy involved

  
  

  This energy depends on the intrinsic properties of the chemical (pKa, pKb, redox potential…).

   

  
  

• 

  the time of exposure.

  
  

  The contact surface and the initial conditions of the tissues (healthy or already damaged) are important too.

   

  
  

The severity of chemical burns is also linked to physical factors such as pressure and temperature, the body area in contact with the chemical, the extent of the damage and the condition of the damaged tissues, whether they are or are not healthy.
The effectiveness of the management of the emergent decontamination and of the primary care determines the onset and development of a chemical burn and, as a result, the extent of the sequelae. (1)

(1) Mathieu L, Burgher F, Blomet J. Comparative evaluation of the active eye and skin chemical splash decontamination solutions Diphoterine^® and Hexafluorine^® with water and other rinsing solutions: Effects on burn severity and healing [Comparaison des solutions actives de décontamination des projections chimiques Diphotérine^® et Hexafluorine^® avec l’eau et d’autres solutions de lavage : impacts sur la sévérité des brûlures et la cicatrisation]. Journal Chemical Health And Safety, 2007, 14, N°4, 32-39

Diagram

The following diagram gathers all the elements mentioned above.
The consequences induced by a chemical splash depend on the precocity and quality of its management.